Some current state of the art photolithography techniques use 193 nanometers ultraviolet (UV) light sources to image patterns onto silicon substrates. This type of technique can produce technology nodes (e.g., size of smallest feature, such as ½ pitch of parallel lines) that are about 200-250 nanometers in size. However, faster and more complex integrated circuits continuously demand smaller nodes. An immersion photolithography makes some improvement in this regard and allows production of 45 nanometer nodes and even 32 nanometer nodes. In an immersion photolithography, a final lens of the lithography system and the sample are both immersed into a liquid medium, such as water. This arrangement, in turn, can create many processing issues.
Other “next generation” photolithography techniques have been recently proposed to produce even smaller nodes. Some promising examples include extreme ultraviolet (EUV) lithography, X-ray lithography, electron beam lithography, focused ion beam lithography, and nano-imprint lithography. These new approaches can result in new challenges. For example, nano-imprint lithography can produce bubble defects, while EUV lithography can be very susceptible to even minor mask defects.